Clinical utility of indium 111-capromab pendetide immunoscintigraphy in the detection of early, recurrent prostate carcinoma after radical prostatectomy

Prostate Cancer-PET Imaging Update

Prostate cancer is the most common non-dermatologic cancer in men, and one of the leading causes of cancer-related mortality. The incidence of prostate cancer increases precipitously after the age of 65 and demonstrates variable aggressiveness, depending on its grade and stage at diagnosis. Despite recent advancements in prostate cancer treatment, recurrence is seen in 25% of patients. Advancements in prostate cancer Positron Emission Tomography (PET) molecular imaging and recent United States Food and Drug Administration (FDA) approvals have led to several new options for evaluating prostate cancer. This manuscript will review the commonly used molecular imaging agents, with an emphasis on Fluorine-18 fluciclovine (Axumin) and PSMA-ligand agents, including their protocols, imaging interpretation, and pitfalls.

Gallium and indium complexes with new hexadentate bis(semicarbazone) and bis(thiosemicarbazone) chelators

The synthesis of two new hexadentate potentially tetra-anionic acyclic chelators, an N2O4-donor bis(semicarbazone) (H4bsc) and an N2O2S2-donor bis(thiosemicarbazone) (H4btsc), is described. Coordination reactions of the ligands with gallium and indium precursors were investigated and yielded the complexes [Ga(Hbsc)] (1) and [In(Hbtsc)] (2), respectively. Ligands and complexes structures were confirmed by several techniques, including FTIR, NMR (1H, 13C, COSY, HSQC), ESI(+)-MS and single crystal X-ray diffraction analysis. The radioactive congeners [67Ga(Hbsc)] (1*) and [111In(Hbtsc)] (2*) were also synthesized and their radiolabeling yield and radiochemical purity were certified by HPLC and ITLC analyses. Biodistribution assays in groups of CD-1 mice showed a high uptake of both radiocomplexes in liver and intestine where 1* presented higher retention. In vitro and in vivo assays revealed higher stability of 1* compared with 2*, namely in the blood. The results suggest that radiocomplex 1* is a candidate for further investigation as it could be prepared in high yields (>95%), at low temperature (20-25 °C) and at fast reaction time (15 min), which are very desirable synthesis conditions for potential new radiopharmaceuticals.

Imaging of local recurrence in prostate cancer

Diagnosis of prostate cancer (PCa) recurrence after therapy with curative intent currently depends primarily on biochemical serum analyses. When recurrence is suspected, further treatment decisions rely heavily on the confirmation of disease presence and determination of its extent. This is complicated by the fact that benign conditions can mimic biochemical recurrence, and serum studies do not reliably discriminate between local and distant recurrence. This review discusses the contemporary imaging paradigm for the evaluation of local PCa recurrence. The multidisciplinary implications for urologists, radiation oncologists and radiologists are examined. Emerging techniques and future directions of PCa imaging research are discussed.

Use of radiopharmaceuticals in diagnostic nuclear medicine in the United States: 1960-2010

To reconstruct reliable nuclear medicine-related occupational radiation doses or doses received as patients from radiopharmaceuticals over the last five decades, the authors assessed which radiopharmaceuticals were used in different time periods, their relative frequency of use, and typical values of the administered activity. This paper presents data on the changing patterns of clinical use of radiopharmaceuticals and documents the range of activity administered to adult patients undergoing diagnostic nuclear medicine procedures in the U.S. between 1960 and 2010. Data are presented for 15 diagnostic imaging procedures that include thyroid scan and thyroid uptake; brain scan; brain blood flow; lung perfusion and ventilation; bone, liver, hepatobiliary, bone marrow, pancreas, and kidney scans; cardiac imaging procedures; tumor localization studies; localization of gastrointestinal bleeding; and non-imaging studies of blood volume and iron metabolism. Data on the relative use of radiopharmaceuticals were collected using key informant interviews and comprehensive literature reviews of typical administered activities of these diagnostic nuclear medicine studies. Responses of key informants on relative use of radiopharmaceuticals are in agreement with published literature. Results of this study will be used for retrospective reconstruction of occupational and personal medical radiation doses from diagnostic radiopharmaceuticals to members of the U.S. radiologic technologists' cohort and in reconstructing radiation doses from occupational or patient radiation exposures to other U.S. workers or patient populations.

A paradigm shift from anatomic to functional and molecular imaging in the detection of recurrent prostate cancer

Approximately a third of men with localized prostate cancer who are treated with external beam radiation therapy (EBRT) or radical prostatectomy (RP) develop biochemical failure (BF). Presumably, BF will progress to distant metastasis and prostate cancer-specific mortality in some patients over subsequent years. Accurate detection of recurrent disease is important because it allows for appropriate treatment selection (e.g., local vs systemic therapy) and early delivery of therapy (e.g., salvage EBRT), which affect patient outcome. In this article, we discuss the paradigm shift in imaging technology in the detection of recurrent prostate cancer. First, we discuss the commonly used morphological and anatomical imaging modalities and their role in the post-RP and post-EBRT settings of BF. Second, we discuss the accuracy of functional and molecular imaging techniques, many of which are under investigation. Further studies are needed to establish the role of imaging techniques for detection of cancer recurrence and clinical decision-making.

Salvage Low-Dose-Rate Brachytherapy for Prostate Cancer Local Recurrence after Radical Prostatectomy: Our First three Patients

Purpose of the Study

To present our initial experience with brachytherapy (BT) as a primary salvage procedure for the treatment of prostate cancer (PCa) local recurrence following radical retropubic prostatectomy (RRP).

Methods

From December 2009 to May 2010, three patients underwent salvage BT due to local recurrences of high risk PCa after extrafascial RRP without additional adjuvant therapies. Local recurrence was confirmed by prostate biopsy and the relapse was well defined by endorectal ultrasonography and magnetic resonance imaging. Metastatic screening was negative. The patients were followed-up according to the American Brachytherapy Society guidelines.

Results

The median dose delivered to 90% of the local relapse (D90) was 115 Gy. The three patients reached a prostate specific antigen (PSA) nadir value within the first year that remained stable at a mean follow-up of 32 months. As regards morbidity, moderate de novo urgency was reported by only one patient.

Conclusions

We think that our data confirms the feasibility and safety of salvage BT as a possible alternative option to external beam radiotherapy (EBRT) for the treatment of locally recurrent PCa in selected patients when performed by experienced centers. However, larger series of patients with longer follow-ups are needed to define the oncologic role of this procedure.

Role of magnetic resonance imaging in the detection of local prostate cancer recurrence after external beam radiotherapy and radical prostatectomy

AIMS

To carry out a meta-analysis to assess the effectiveness of magnetic resonance imaging (MRI) during the follow-up of patients with prostate cancer after undergoing external beam radiotherapy (EBRT) or radical prostatectomy.

MATERIALS AND METHODS

MEDLINE, EMBASE and other databases were searched for relevant original articles published from January 1995 to October 2011. Methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. Pooled estimation and subgroup analysis data were obtained by statistical analysis.

RESULTS

Fourteen of 768 initially identified studies were included in the meta-analysis. Seven studies examining patient after radical prostatectomy had a pooled sensitivity and specificity on the patient level of 82% (95% confidence interval 78-86%) and 87% (95% confidence interval 81-92%), respectively. In the subgroup analysis, compared with T2-weighted imaging (T2WI), dynamic contrast-enhanced (DCE) MRI showed higher pooled sensitivity (85%, 95% confidence interval 78-90%) and specificity (95%, 95% confidence interval 88-99%). DCE MRI combined with magnetic resonance spectroscopic imaging (1H-MRSI) had the highest pooled sensitivity (92%, 95% confidence interval 83-97%). Nine studies examining men after EBRT had a pooled sensitivity and specificity on the patient level of 82% (95% confidence interval 75-88%) and 74% (95% confidence interval 64-82%), respectively. Compared with T2WI, DCE MRI showed higher pooled sensitivity (90%, 95% confidence interval 77-97%) and specificity (81%, 95% confidence interval 64-93%). DCE combined with 1H-MRSI had the highest pooled specificity (90%, 95% confidence interval 56-100%). The pooled sensitivity and specificity on sextant analysis was 58% (95% confidence interval 53-64%) and 85% (95% confidence interval 82-88%), respectively. DCE MRI showed the highest pooled sensitivity: 71% (95% confidence interval 60-80%).

CONCLUSION

A limited number of small studies suggest that MRI can accurately detect local recurrences after EBRT and radical prostatectomy. DCE MRI is particularly accurate. The addition of MRSI to DCE MRI can significantly improve the diagnostic accuracy of local prostate cancer recurrence. The eventual role of 1H-MRSI alone remains controversial and needs to be defined further.

Radiation therapy for prostate cancer after prostatectomy: adjuvant or salvage?

Approximately 15-25% of men who undergo radical prostatectomy for localized prostate cancer will experience a PSA-defined biochemical recurrence (BCR) of their cancer--men with poorly differentiated cancer, non-organ-confined disease, and positive surgical margins are at the highest risk. Accumulating evidence indicates that postoperative radiation therapy to the prostate bed favorably influences the course of disease in men with pathological features of poor prognosis. Three phase III randomized trials of adjuvant radiotherapy versus observation have reported improved freedom from BCR, and one study has reported improved metastasis-free survival and overall survival. Similar evidence from randomized trials for salvage radiotherapy is lacking; however, several observational studies have reported durable responses to salvage radiotherapy and reduced cancer-specific mortality in a substantial proportion of high-risk patients, provided that it is administered at the earliest evidence of BCR. The appeal of salvage radiotherapy is that a substantial proportion of patients with non-organ-confined cancer or positive surgical margins are cured after radical prostatectomy alone, thereby limiting the adverse effects of postoperative radiotherapy--which include urinary and bowel dysfunction, sexual dysfunction and secondary pelvic malignancies--to only those whose cancer was not cured by surgery. In the absence of data from randomized trials demonstrating the superiority of adjuvant radiotherapy over a surveillance strategy (with planned salvage radiotherapy at the earliest evidence of BCR), we advocate shared decision making between physicians and patients, based on the relative advantages and disadvantages of each approach.

An interobserver study of prostatic fossa clinical target volume delineation in clinical practice: are regions of recurrence adequately targeted?

OBJECTIVES

To study interphysician variability of delineation of the prostatic fossa clinical target volume (pfCTV) to be irradiated in patients with residual or recurrent microscopic prostate cancer following radical prostatectomy and to estimate the risk for a geographical miss.

METHODS

Thirty-eight pfCTV were delineated on postradical prostatectomy computerized tomography scans of 8 patients by 5 observers. To estimate the risk of a geographical miss, a high risk volume (HRV) was defined and the percentage of "missed" HRV was calculated for each pfCTV.

RESULTS

Interphysician variability was considerable with a mean pfCTV of 39.09 cm (range, 11.8-72.5 cm). At least 25% of the HRV at the bladder neck/anastomosis and the retro-vesical space was excluded in 11 pfCTVs. The mean "missed" HRV was 27.5% (range, 2.3%-78.7%). A pfCTV of less than 30 cm was associated with a geographical miss in 66% of cases versus 17.2% for pfCTV of 30 cm or more (P = 0.006). Observer identity was significantly associated with excluded HRV (P = 0.03).

CONCLUSIONS

pfCTV delineation is subject to considerable interobserver variability associated with a significant risk of inadequate targeting of the anastomosis/bladder neck region and the retrovesical space. The failure to recognize regions at high risk for harboring microscopic disease may be due to a lack of familiarity with tissue redistribution following radical surgery, and a lack of literature-based guidelines for pfCTV delineation. A strategy to improve pfCTV delineation is proposed.

Salvage radiotherapy for patients with PSA relapse following radical prostatectomy: issues and challenges

A progressively rising level of serum prostate specific antigen (PSA) after radical prostatectomy (RP) invariably indicates the recurrence of prostate cancer. The optimal management of patients with post-RP PSA relapse has remained uncertain due to a wide variability in the natural course of post-RP PSA relapse and the inability to separate a recurrent disease confined to the prostate bed from that with occult distant metastasis. Management uncertainty is further compounded by the lack of phase III clinical studies demonstrating which therapeutic approach, if any, would prolong life with no significant morbidity. Radiotherapy has been the main therapeutic modality with a curative potential for patients with post-RP PSA relapse. This review article depicts issues and challenges in the management of patients with post-RP PSA relapse, presents the literature data for the efficacy of salvage radiotherapy, either alone or in combination of androgen ablation therapy, and discusses future directions that can optimize treatment strategies.

111-In-capromab pendetide imaging using hybrid-γ camera-computer tomography technology is not reliable in detecting seminal vesicle invasion in patients with prostate cancer

OBJECTIVES

In this study, we evaluate the diagnostic utility of a hybrid γ-camera-computer tomography (SPECT-CT) indium-111 (111-In)-capromab pendetide scan in detecting seminal vesicle invasion (SVI) in select patients evaluated for primary surgical treatment of prostate cancer (CaP).

METHODS AND MATERIALS

We retrospectively analyzed a prospective database of patients who underwent preoperative SPECT-CT imaging with 111-In-capromab-pendetide as part of a staging evaluation who were subsequently treated with radical surgery in our center. Only patients with clinically localized disease were included. We calculated diagnostic properties of the hybrid scan in detecting SVI compared with final pathology. Regression analyses were performed, including scan and preoperative variables to predict SVI.

RESULTS

We retrieved 50 medical records matching our criteria. Median patient age was 61 years (range 45-74). Most patients had a clinical T1c CaP and biopsy Gleason score of 7 or higher. On final pathology, SVI was found in 12 (24%) specimens and radiotracer signal in the seminal vesicle region was reported in 15 (30%) imaging studies. Hybrid SPECT-CT imaging had a sensitivity of 25%, specificity of 61.9%, positive and negative predictive values of 20% and 74.3%, respectively, for detecting SVI. SPECT-CT results did not contribute significantly to SVI prediction on univariate (P = 0.627) or multivariate (P = 0.754) analyses.

CONCLUSIONS

SPECT-CT imaging with 111-In-capromab-pendetide is not reliable in detecting or excluding SVI in this select cohort. High rates of positive radiotracer signals from healthy seminal vesicles raise concerns regarding pharmacologic properties of this radiotracer molecule.

[Which imaging methods should be used prior to salvage radiotherapy after prostatectomy for prostate cancer?]

Prostatectomy is one of the most widely used methods for treatment of adenocarcinoma of the prostate. According to anatomopathological criteria, between 10 and 40% of patients will display biochemical relapse in the absence of adjuvant radiotherapy. Anatomopathological and biochemical criteria are powerful tools for selecting patients for salvage radiotherapy. The aim of this article is to review literature on the latest progress in radiological and nuclear medicine techniques and their performance levels, in order to determine local, regional and metastatic relapses associated with the techniques and specify the radiotherapy target volume. Magnetic resonance imaging (MRI) displays the best sensitivity and specificity for examination of the prostate bed and enables simultaneous assessment of the pelvic region - thus diminishing the utility of computed tomography. The performance levels of MRI will probably continue to improve, with the use of dynamic MRI and MR spectroscopy. Despite the development of new markers like (11)C and (18)F choline and acetate, the sensitivity of positron emission tomography is still low. Prospective studies with an appropriate methodology are necessary for specifying the technique's value in this context.

Diagnostic evaluation of PSA recurrence and review of hormonal management after radical prostatectomy

The aim of this review is to provide a discussion of the diagnostic evaluation of biochemical recurrence following radical prostatectomy (RP) and an overview of the postoperative hormonal treatment (HT) options. As no randomized trials in the clinical setting of postoperative prostate-specific antigen recurrence have been reported, there is no conclusive evidence that HT after RP will prolong survival or reduce morbidity. Non-traditional approaches, such as intermittent androgen deprivation, non-steroidal anti-androgens and combination of finasteride and non-steroidal anti-androgen, are investigated and may be acceptable options. Combinations of HT with radiotherapy and/or chemotherapy for treatment of recurrent prostate cancer are under study.

Role of dynamic contrast-enhanced magnetic resonance (MR) imaging and proton MR spectroscopic imaging in the detection of local recurrence after radical prostatectomy for prostate cancer

OBJECTIVES

To assess the accuracy of magnetic resonance (MR) spectroscopic imaging (1H-MRSI) and dynamic contrast-enhanced MR (DCEMR) in the depiction of local prostate cancer recurrence in patients with biochemical progression after radical prostatectomy (RP).

MATERIALS AND METHODS

1H-MRSI and DCEMR were performed in 70 patients at high risk of local recurrence after RP. The population was divided on the basis of the clinical validation of MR results with the use of a transrectal ultrasound biopsy examination in a group of 50 patients (group A) and the prostate-specific antigen (PSA) serum level restitution after external beam radiotherapy, in a group of 20 patients (group B).

RESULTS

In group A, 1H-MRSI analysis alone showed a sensitivity of 84% and a specificity of 88%; the DCEMR analysis alone, a sensitivity of 71% and a specificity of 94%; combined 1HMRSI-DCEMR, a sensitivity of 87% and specificity of 94%. Areas under the receiver operating characteristic (ROC) curve for 1HMRSI, DCEMR, and combined 1HMRSI /DCEMR were 0.942, 0.93,1 and 0.964, respectively. In group B, 1HMRSI alone showed a sensitivity of 71% and a specificity of 83%; DCEMR, a sensitivity of 79% and a specificity of 100%; combined 1HMRSI and DCEMR, a sensitivity of 86% and a specificity of 100%. Areas under the ROC curve for each of these groups were 0.81, 0.923, and 0.94, respectively.

CONCLUSION

Our results show that combined 1H-MRSI and DCMRE is an accurate method to identify local prostate cancer recurrence in patients with biochemical progression after RP.

Anatomic boundaries of the clinical target volume (prostate bed) after radical prostatectomy

PURPOSE

We sought to derive and validate an interdisciplinary consensus definition for the anatomic boundaries of the postoperative clinical target volume (CTV, prostate bed).

METHODS AND MATERIALS

Thirty one patients who had planned for radiotherapy after radical prostatectomy were enrolled and underwent computed tomography and magnetic resonance imaging (MRI) simulation prior to radiotherapy. Through an iterative process of consultation and discussion, an interdisciplinary consensus definition was derived based on a review of published data, patterns of local failure, surgical practice, and radiologic anatomy. In validation, we analyzed the distribution of surgical clips in reference to the consensus CTV and measured spatial uncertainties in delineating the CTV and vesicourethral anastomosis. Clinical radiotherapy plans were retrospectively evaluated against the consensus CTV (prostate bed).

RESULTS

Anatomic boundaries of the consensus CTV (prostate bed) are described. Surgical clips (n = 339) were well distributed throughout the CTV. The vesicourethral anastomosis was accurately localized using central sagittal computed tomography reconstruction, with a mean +/- standard deviation uncertainty of 1.8 +/- 2.5 mm. Delineation uncertainties were small for both MRI and computed tomography (mean reproducibility, 0-3.8 mm; standard deviation, 1.0-2.3); they were most pronounced in the anteroposterior and superoinferior dimensions and at the superior/posterior-most aspect of the CTV. Retrospectively, the mean +/- standard deviation CTV (prostate bed) percentage of volume receiving 100% of prescribed dose was only 77% +/- 26%.

CONCLUSIONS

We propose anatomic boundaries for the CTV (prostate bed) and present evidence supporting its validity. In the absence of gross recurrence, the role of MRI in delineating the CTV remains to be confirmed. The CTV is larger than historically practiced at our institution and should be encompassed by a microscopic tumoricidal dose.

Development of radioimmunotherapeutic and diagnostic antibodies: an inside-out view

Only a handful of radiolabeled antibodies (Abs) have gained US Food and Drug Administration (FDA) approval for use in clinical oncology, including four immunodiagnostic agents and two targeted radioimmunotherapeutic agents. Despite the advent of nonimmunogenic Abs and the availability of a diverse library of radionuclides, progress beyond early Phase II radioimmunotherapy (RIT) studies in solid tumors has been marginal. Furthermore, [18F]fluorodeoxyglucose continues to dominate the molecular imaging domain, underscored by a decade-long absence of any newly approved Ab-based imaging agent (none since 1996). Why has the development of clinically successful Abs for RIT been limited to lymphoma? What obstacles must be overcome to allow the FDA approval of immuno-positron emission tomography (immuno-PET) imaging agents? How can we address the unique challenges that have thus far prevented the introduction of Ab-based imaging agents and therapeutics for solid tumors? Many poor decisions have been made regarding radiolabeled Abs, but useful insight can be gained from these mistakes. The following review addresses the physical, chemical, biological, clinical, regulatory and financial limitations that impede the progress of this increasingly important class of drugs.

Operative probe scintimetry with indium and technetium for colorectal cancer

Surgeons introduced the hand-held gamma detection probe in combination with tumor-directed monoclonal antibodies in patients with colorectal cancer. The clinicians conducted innovative research involving antibody chemistry and variation as well as radioactive dosimetry and decay. The results of these studies represented an era when surgeons began reporting on specific lesion detection and the impact of the antibody administration on the management of the patient. The summary of the important early trials involving monoclonal antibodies and probe scintimetry provides a valuable look into the early development of the antibody technology and a glimpse of potential future applications using the gamma detection probe.

Management of asymptomatic rise in prostatic-specific antigen in patients with prostate cancer

Biochemical failure after curative-intent therapies is an increasingly common dilemma confronting patients and physicians. No definition of biochemical failure exists that can be applied to all forms of treatment and that is not to some degree affected by the follow-up interval, pretreatment prognostic factors, or the frequency of prostatic-specific antigen (PSA) testing. Available imaging techniques lack sensitivity in detection of occult micrometastases. Prognostic factors such as tumor characteristics and PSA kinetics should be considered when recommending second-line therapies. For those patients with suspected localized recurrence, second-line treatment with salvage therapies may provide long-term disease control. Hormonal therapy, although most commonly employed for PSA recurrence, is of palliative benefit only. Currently, the most appropriate therapeutic intervention for asymptomatic patients with evidence of biochemical failure remains undefined.

Long-term follow-up of 111In-capromab pendetide (ProstaScint) scan as pretreatment assessment in patients who undergo salvage radiotherapy for rising prostate-specific antigen after radical prostatectomy for prostate cancer

PURPOSE

To evaluate the long-term failure patterns in patients who underwent an (111)In-capromab pendetide (ProstaScint) scan as part of their pretreatment assessment for a rising prostate-specific antigen (PSA) level after prostatectomy and subsequently received local radiotherapy (RT) to the prostate bed.

METHODS

Fifty-eight patients were referred for evaluation of a rising PSA level after radical prostatectomy. All patients had negative findings for metastatic disease after abdominal/pelvis imaging with CT and isotope bone scans. All patients underwent a capromab pendetide scan, and the sites of uptake were noted. All patients were treated with local prostate bed RT (median dose 66.6 Gy).

RESULTS

Of the 58 patients, 20 had biochemical failure (post-RT PSA level >0.2 ng/mL or a rise to greater than the nadir PSA), including 6 patients with positive uptake outside the bed (positive elsewhere). The 4-year biochemical relapse-free survival (bRFS) rates for patients with negative (53%), positive in the prostate bed alone (45%), or positive elsewhere (74%) scan findings did not differ significantly (p = 0.51). The positive predictive value of the capromab pendetide scan in detecting disease outside the bed was 27%. The capromab pendetide scan status had no effect on bRFS. Those with a pre-RT PSA level of <1 ng/mL had improved bRFS (p = 0.003).

CONCLUSION

The capromab pendetide scan has a low positive predictive value in patients with positive elsewhere uptake and the 4-year bRFS was similar to that for those who did not exhibit positive elsewhere uptake. Therefore, patients with a postprostatectomy rising PSA level should considered for local RT on the basis of clinicopathologic factors.

Endorectal MRI assessment of local relapse after surgery for prostate cancer: A model to define treatment field guidelines for adjuvant radiotherapy in patients at high risk for local failure

PURPOSE

To assess the role of endorectal magnetic resonance imaging (MRI) in defining local relapse after radical prostatectomy for prostate cancer to help to reassess the clinical target volume (CTV) for adjuvant postprostatectomy radiotherapy.

METHODS AND MATERIALS

Sixty patients undergoing an endorectal MRI before salvage radiotherapy were selected. Spatial coordinates of the relapses were assessed using two reference points: the inferior border of the pubic symphysis (point 1) and the urethro-vesical anastomosis (point 2). Every lesion on MRI was delineated on the planning computed tomography and center of mass coordinates were plotted in two separate diagrams (along the x, y, and z axes) with the urethro-vesical anastomosis as the coordinate origin. An "ideal" CTV was constructed, centered at a point defined by the mathematical means of each of the three coordinates with dimensions defined as twice 2 standard deviations in each of the three axes. The dosimetric impact of the new CTV definition was evaluated in six adjuvantly treated patients.

RESULTS

The ideal CTV center of mass was located at coordinates 0 (x), -5 (y), and -3 (z) mm with SDs of 6 (x), 6 (y), and 9 (z) mm, respectively. The CTV size was 24 (x) x 24 (y) x 36 (z) mm. Significant rectal sparing was observed with the new CTV.

CONCLUSIONS

A CTV with an approximately cylindrical shape (approximately 4 x 3 cm) centered 5 mm posterior and 3 mm inferior to the urethro-vesical anastomosis was defined. Such CTV may reduce the irradiation of normal nontarget tissue in the pelvis potentially improving treatment tolerance.

Validation of 8-[123I]iodo-L-1,2,3,4-tetrahydro-7-hydroxyisoquinoline-3-carboxylic acid as an imaging agent for prostate cancer in experimental models of human prostate cancer

INTRODUCTION

Very few tracers are currently available for the detection and staging of prostate cancer with positron emission tomography and single-photon emission computed tomography. This study evaluates the potential of 8-[123I]iodo-1,2,3,4-tetrahydro-7-hydroxyisoquinoline-3-carboxylic acid [ITIC(OH)] as an imaging agent for prostate cancer in experimental models of human prostate cancer.

METHODS

ITIC(OH) was prepared by the IODO-GEN method, with 82+/-7% radiochemical yield and >99% radiochemical purity after high-performance liquid chromatography. Thereafter, ITIC(OH) was examined in CD-1 nu/nu mice engrafted with human PC-3 and DU-145 prostate cancer in the flank or orthotopically in the prostate. Bioevaluation involved examination of the in vivo stability and uptake characteristics of ITIC(OH) into tumors and different organs by dynamic in vivo analysis and gamma counting of organs of interest after dissection.

RESULTS

ITIC(OH) showed good in vivo stability for biological investigations and was primary cleared through urine. In vivo, ITIC(OH) accumulated highly and specifically in tumors, reaching 13.6+/-2.1% to 16.2+/-2.5% injected dose per gram (ID/g) in heterotopic tumors compared with 14.8+/-2.6% and 17.6+/-3.4% ID/g in orthotopic tumor engrafts at 60 and 240 min postinjection, respectively. In contrast, radioactivity uptake in the blood, spleen, liver and gastrointestinal tract was moderate and decreased with time, resulting in marked tumor-to-background and excellent visualization of tumors.

CONCLUSION

These results suggest that ITIC(OH) is a promising candidate as radiotracer for detecting prostate cancer and warrants further studies in patients to ascertain its potential as an imaging agent for clinical use.

Enhancing the utility of prostascint SPECT scans for patient management

This project investigated reducing the artifact content of In-ill ProstaScint SPECT scans for use in treatment planning and management. Forty-one patients who had undergone CT or MRI scans and simultaneous Tc-99m RBC/In-111 ProstaScint SPECT scans were included. SPECT volume sets, reconstructed using Ordered Set-Expectation Maximum (OS-EM) were compared against those reconstructed with standard Filtered Back projection (FBP). Bladder activity in Tc-99m scans was suppressed within an ellipsoidal volume. Tc-99m voxel values were subtracted from the corresponding In-111 after scaling based on peak activity within the descending aorta. The SPECT volume data sets were merged with the CT or MRI scans before and after processing. Volume merging, based both on visual assessment and statistical evaluation, was not affected. Thus iterative reconstruction together with bladder suppression and blood pool subtraction may improve the interpretation and utility of ProstaScint SPECT scans for patient management.

Therapy with immunoglobulin: applications for monoclonal antibodies

The ability of antibodies to recognize specific antigenic targets and trigger responses from the immune system has made them attractive candidates as therapeutic agents. Monoclonal and recombinant technology have made possible the development of a new class of therapeutic and diagnostic agents that combine the exquisite specificity of antibodies with biologic compatibility and protracted half-lives. This technology is just beginning to be explored and considerable evolution may be expected in the next few decades.

Postprostatectomy target-normal structure overlap volume differences using computed tomography and radioimmunoscintigraphy images for radiotherapy treatment planning

PURPOSE

The purpose of this study was to analyze regions of uptake in normal structures on postprostatectomy radioimmunoscintigraphy (RIS) images by evaluating differences in the overlap volumes of prostate fossa clinical target volume (CTV) and planning target volume (PTV) using correlative computed tomography (CT) images.

MATERIALS AND METHODS

The electronic records of 13 patients who received external beam radiotherapy postprostatectomy and who underwent a vessel-based RIS/CT registration were reviewed. For each patient, the RIS-defined CTV (CTV(RIS)) was compared (in terms of the overlap volume with the surrounding bladder, rectum, pubic symphysis, and penile bulb) with the CT-defined CTV(pre) before this registration and also with CTV(post) (the final target volume used for treatment). Similar analyses were done for PTV(RIS), PTV(pre), and PTV(post) defined in each case to be the corresponding CTV + 1-cm margin.

RESULTS

CTV(RIS) overlapped significantly more with the bladder, rectum, and symphysis, but not with the penile bulb, than did either the CTV(pre) or CTV(post). However, the corresponding PTV analyses revealed no significant differences between any of the overlap volumes of any of the PTVs with the bladder, rectum, and penile bulb, but did reveal a significant difference between the PTV(RIS) and PTV(post) overlap volumes with the symphysis compared with PTV(pre) overlap volumes with the symphysis.

CONCLUSIONS

On RIS images, there appear to be areas of uptake in the bladder, rectum, and pubic symphysis but not the penile bulb; however, the dosimetric consequences of this uptake for radiation treatment planning are minimal on the bladder, rectum, and penile bulb, but require segmentation for dose reduction to the pubic symphysis.

The Impact of a Negative 111 Indium-Capromab Pendetide Scan Before Salvage Radiotherapy

PURPOSE

We determined the prognostic role, if any, of the ProstaScint (111)indium-capromab pendetide scan before salvage radiotherapy for biochemical recurrence after RP for localized prostate cancer.

MATERIALS AND METHODS

We reviewed the records of 649 patients who underwent a ProstaScint scan from 1998 to 2004. A total of 44 patients were identified who had biochemical recurrence after RP and underwent a ProstaScint scan immediately before salvage radiotherapy. All patients received salvage radiotherapy to the prostatic bed unless pelvic lymph node uptake was identified on the scan, resulting in initial whole pelvic radiotherapy with 45 Gy, followed by a conformal boost to the prostate bed in 6. The median salvage radiotherapy dose to the prostate bed was 72 Gy. Patient demographics, pathological information, PSA values and ProstaScint results were collected retrospectively. The majority of ProstaScint scans were digitally fused with noncontrast pelvic computerized tomography images for interpretation. PSA progression after radiotherapy was defined using American Society for Therapeutic Radiation and Oncology criteria.

RESULTS

At a mean followup of 22 months 43 of 44 patients (97%) experienced a PSA decrease after salvage radiotherapy with a mean PSA nadir of 0.16 ng/ml compared to a mean pre-radiotherapy PSA of 1.7 ng/ml. Of the 44 patients 15 (34%) showed post-radiotherapy PSA progression. When the entire cohort was analyzed, patients with negative ProstaScint scans had statistically lower post-radiotherapy PSA progression rates than patients with positive scans (1 of 10 or 10% vs 14 of 34 or 41%, p = 0.026). Patients with negative ProstaScint results were also statistically more likely to have a pre-radiotherapy PSA of less than 1.0 ng/ml (p = 0.005), no seminal vesicle involvement (p = 0.006), a greater mean PSA doubling time (p = 0.008) and received no hormone therapy (p = 0.003). When patients with pre-radiotherapy PSA less than 1.0 ng/ml were analyzed, a negative ProstaScint scan suggested but did not provide a statistically significant advantage over pre-radiotherapy PSA alone for predicting post-radiotherapy PSA progression (1 of 9 or 11% for negative vs 5 of 15 or 33% for positive scans, p = 0.20).

CONCLUSIONS

Our early experience supports an improved prognosis in patients receiving salvage pelvic radiotherapy for biochemical recurrence after RP who have a negative pre-radiotherapy ProstaScint scan. However, this finding is not necessarily independent of pre-radiotherapy PSA.

Biochemical Recurrence after Localized Treatment

The quoted incidence of biochemical recurrence (BCR) after localized treatment varies significantly and depends on numerous well-known prognostic factors; however, it likely occurs in at least 30%-40% of patients who receive localized treatment. Because the clinical significance of BCR is often unclear, and depends in many cases on unknown factors, it is difficult to select the best treatment and determine when best to institute that therapy. This review examines some of the issues associated with BCR and attempts to shed some light on this common but controversial clinical scenario. Some treatment strategies discussed in this article include salvage radiotherapy after radical prostatectomy, salvage therapy after radiotherapy, and hormonal therapy.

The value of radiotherapy in treating recurrent prostate cancer after radical prostatectomy

Approximately 25-40% of men who undergo radical retropubic prostatectomy (RRP) for the treatment of clinically localized prostate cancer will experience biochemical recurrence. A rapid prostate-specific antigen (PSA) doubling time or high-grade disease are risk factors for progression to bone metastases and cancer-specific mortality. Salvage external-beam radiotherapy (EBRT) to the prostate fossa is the only curative therapy for patients with biochemical recurrence after RRP, but it is used relatively infrequently to treat recurrent prostate cancer because of a widespread perception that most patients have systemic recurrence, and its reported lack of efficacy for high-risk disease. However, in a large, multicenter study of patients who received salvage EBRT for a rising PSA level after RRP, a substantial proportion of patients with high-grade disease and/or a rapid PSA doubling time were observed to have a favorable outcome after salvage EBRT if it was administered at low PSA values. This suggests that salvage EBRT could provide long-term cancer control for patients at the highest risk of progression to bone metastases and cancer-specific mortality. A nomogram that predicts the 3-year progression-free probability after salvage EBRT has been developed to facilitate the selection of patients for this potentially curative therapy. In the absence of other curative therapies, all patients with recurrent prostate cancer should be considered for salvage EBRT, particularly those with positive surgical margins. To be successful, salvage EBRT should be administered at the earliest evidence of recurrent disease, once a rising PSA trend as been confirmed.

Parameters for Treatment Decisions for Salvage Radiation Therapy

Radical prostatectomy (RP) is the most common primary treatment for prostate cancer. About 40% of those with high-risk pathologic features, such as a positive margin or seminal vesicle involvement, will develop biochemical failure at some point in the future. Radiotherapy (RT), with or without concurrent androgen deprivation, has been used liberally in the management of men with a rising prostate-specific antigen (PSA) after RP, based mostly on relatively small retrospective series. Factors such as the prostatectomy Gleason score, seminal vesicle invasion, absolute pre-RT PSA level, and pre-RT PSA doubling time are emerging as important determinants of outcome after RT. These factors should be used as a guide to the options of local therapy alone (RT), local therapy plus systemic therapy (typically androgen deprivation therapy), and systemic therapy alone.

Radiolabeled peptides in oncology: role in diagnosis and treatment

There has been an exponential growth in the development of radiolabeled peptides for diagnostic and therapeutic applications in the last decade. The automated means of synthesizing these compounds in large quantities and the simplified methods of purifying, characterizing, and optimizing them have kindled attention to peptides as carrier molecules. These new techniques have accelerated the commercial development of radiolabelled peptides, which has provided additional radiopharmaceuticals for the nuclear medicine community. Peptides have many key properties including fast clearance, rapid tissue penetration, and low antigenicity, and can be produced easily and inexpensively. However, there may be problems with in vivo catabolism, unwanted physiologic effects, and chelate attachment. Radiolabeled peptides have made their greatest impact in the management of relatively rare neuroendocrine malignancies. Indeed, Indium-111 ((111)In)-pentetreotide ((111)In-DTPA-octreotide, Octreoscan), which binds to somatostatin receptors (SSTRs), has become the diagnostic 'gold standard' in these diseases. However, (111)In-pentetreotide has been less successful in the diagnosis of other more prevalent diseases in which SSTRs are upregulated. Technetium-99m (99mTc)-depreotide (NeoTect), a 99mTc-labeled SSTR-analog, could have wider impact since it has high sensitivity and specificity for lung cancer lesion detection. However, this impact may be minimized by the increased availability of positron emission tomography imaging with Fluorine-18 (18F)-flourodeoxyglucose, which has similar sensitivity and specificity for lesion identification in this disease, and is currently more widely used. The receptors for bombesin, alpha-melanocyte-stimulating hormone, neurotensin, and the integrin alpha(v)beta3, are under active investigation as targets for radiolabelled peptides, but are still in the pre-clinical stage. Compounds directed at the cholecystokinin-B/gastrin receptor have shown promising results in clinical trials in humans. Radiolabelled peptide therapy is usually indicated for patients with widespread disease that is not amenable to focused radiation therapy or is refractory to chemotherapy. Phase I/II studies using various radiolabelled peptides (including (111)In-pentetreotide, Yttrium-90 [90Y]-DOTA-Phe1-Tyr3-octreotide, 90Y-DOTA-lanreotide, and Lutetium-177 [177Lu]-DOTA-octreotate) for the treatment of patients with neuroendocrine malignancy are in progress. Over 400 patients have been treated, and the response rate has ranged from 60% to 75%, although few patients have had a complete response. Patients have been given individual doses ranging from 2 to 11 GBq with a slow infusion every 4-8 weeks (up to 12 times). The kidney is the dose-limiting organ and most patients experience a transient decline in blood cell counts. A concomitant infusion of an amino acid mixture can reduce kidney toxicity and increase the effective tumor dose. Other peptides currently under investigation, some of which have shown promising results, include Rhenium-188 (188Re)-P2045 and 90Y-alpha(v)beta3 antagonist.

[PSA recurrence after primary curative therapy--local or systemic? When is a second curative therapy still possible?]

PSA recurrence after primary curative therapy for localized prostate cancer is a common problem. Further curative treatment is only reasonable in the case of local recurrence. Therefore, minimizing the likelihood of metastatic disease is crucial. So far, imaging techniques cannot distinguish between local recurrence and distant metastasis. It is therefore reasonable to orientate on PSA kinetics and pathological criteria. Histologic confirmation of suspected local recurrence after radical prostatectomy before salvage therapy is not required. However, after initial radiation therapy histologic confirmation of suspected isolated local recurrence should be obtained. The optimal treatment for a PSA recurrence depends on the initial therapy and the life-expectancy of the patient.

Update on magnetic resonance imaging, ProstaScint, and novel imaging in prostate cancer

PURPOSE OF REVIEW

Despite marked stage migration, approximately a third of patients with clinically organ-confined prostate cancer will have extracapsular extension on pathological analysis. To improve outcomes further, alternative modalities of determining extraprostatic disease must be investigated beyond the current clinical parameters of digital rectal examination, prostate-specific antigen, and Gleason score. In addition, discerning the location of tumor in patients with biochemical recurrence directly affects treatment choice. This review highlights developments in prostate cancer imaging that may improve staging and treatment planning for prostate cancer patients.

RECENT FINDINGS

Magnetic resonance imaging is most useful in the initial evaluation of men with prostate cancer. Its high specificity for the diagnosis of extracapsular extension is tempered by its low sensitivity. Positron emission tomography is used to assess regional and distant metastasis in many malignancies. Investigation into the most appropriate radiotracer for prostate cancer is paramount in any future applicability. The unique role of ProstaScint has been in evaluating patients with biochemical failure and in trying to discern metastasis before definitive therapy. The addition of spectroscopic imaging and nanoparticle infusion may lead to further improvements. Therefore, in differentiating local versus distant recurrence, appropriate interventions with radiotherapy or hormonal manipulation may be instituted.

SUMMARY

Magnetic resonance imaging, ProstaScint, and to some extent positron emission tomography are all relevant imaging modalities for the evaluation of patients with prostate cancer. Current technological advances in each arena are improving the accuracy of diagnosis. Despite their specific limitations, use in the proper clinical setting may provide essential information to improve management decisions and disease outcomes.

Prostate cancer relapse after therapy with curative intention: a diagnostic and therapeutic dilemma

Prostate cancer is the most common malignant disease and second in causes of cancer death among men in Western Europe and North America. Despite improved surgical and irradiation techniques tumor relapse after curatively intended therapy is not uncommon. Due to the difficulty in discriminating local and systemic progression, it is often difficult to decide what this means for the patient and what kind of second-line treatment has to be given. Modern imaging techniques (MRI with endorectal coil, Choline-PET-CT, ProstaScint-Scan) are used for diagnosis of prostate cancer relapse. Nevertheless, early detection of local tumor relapse and likewise the detection of disseminated tumor cells often fails. To differentiate between local and systemic progression, prognostic factors of the primary tumor (grading, surgical margins, infiltration of the seminal vesicles, lymph node metastases) and PSA kinetics are used. The time from initial treatment to biochemical relapse and PSA doubling time are of highest prognostic relevance. Local progression allows second-line local treatment with potentially curative results (local irradiation after radical prostatectomy, salvage-surgery / cryotherapy / HIFU after irradiation), while in the case of systemic progress a palliative systemic therapy (hormonal treatment, chemotherapy, bisphosphonates) is indicated. Before deciding on the most appropriate therapy, prognostic factors and the patient's individual situation (co-morbidity, life expectancy, individual wishes) should be taken into account.

Biochemical recurrence after definitive prostate cancer therapy. Part I: Defining and localizing biochemical recurrence of prostate cancer*

PURPOSE OF REVIEW

The introduction of prostate-specific antigen into clinical practice heralded a dramatic shift in the epidemiology of prostate cancer. The diagnosis and treatment of lower stage disease in younger men with fewer competing co-morbidities has resulted in a longer period of post-treatment cancer surveillance and the potential for disease recurrence. Life-long periodic prostate-specific antigen testing for biochemical recurrence is standard of care; however, there is no single definition of biochemical recurrence that reliably predicts clinical recurrence. This review explores the complexities of biochemical recurrence, a thorough understanding of which is crucial to making appropriate treatment decisions after primary treatment. It also evaluates the array of diagnostic tests frequently employed when biochemical recurrence has occurred.

RECENT FINDINGS

There is a disconnection between biochemical recurrence and progression to clinical disease. The definition of biochemical recurrence varies both by the prostate-specific antigen cut-point used and by the primary therapy employed. Furthermore, biochemical recurrence by itself appears not to be as reliable a predictor of eventual clinical recurrence as prostate-specific antigen doubling time. Current imaging modalities are rarely useful in localizing disease when biochemical recurrence is first detected.

SUMMARY

The correct interpretation of biochemical recurrence is crucial to treatment decision-making. New data show that prostate-specific antigen doubling time during prostate-specific antigen recurrence may be a valid surrogate for death from the disease. The potential therefore exists for prostate-specific antigen doubling time to be accepted as a trial endpoint, which might accelerate drug approval by the United States Food and Drug Administration.

Molecular Nuclear Imaging: The Radiopharmaceuticals (Review)

Application of the nuclear approach for the detection of inherited diseases is an important goal for nuclear medicine and will likely result in an important breakthrough, which will, hopefully, lead to improved diagnoses of genetic defects and objective evaluations of the efficacy of therapeutic strategies. Although still largely in the research realm, molecular imaging is in the process of emerging as a vital component of the diagnosis of disease and monitoring of the therapy. The clinical research in nuclear medicine has made major advancements in the direction of molecular medicine and targeted therapy. In the past few years, exponential achievements have been accomplished in the development of molecular nuclear imaging agents, as described below.

Positron emission tomography for prostate, bladder, and renal cancer

Prostate cancer, renal cancer, bladder, and other urothelial malignancies make up the common tumors of the male genitourinary tract. For prostate cancer, common clinical scenarios include managing the patient presenting with 1) low-risk primary cancer; 2) high-risk primary cancer; 3) prostate-specific antigen (PSA) recurrence after apparently successful primary therapy; 4) progressive metastatic disease in the noncastrate state; and 5) progressive metastatic disease in the castrate state. These clinical states dictate the appropriate choice of diagnostic imaging modalities. The role of positron emission tomography (PET) is still evolving but is likely to be most important in determining early spread of disease in patients with aggressive tumors and for monitoring response to therapy in more advanced patients. Available PET tracers for assessment of prostate cancer include FDG, 11C or 18F choline and acetate, 11C methionine, 18F fluoride, and fluorodihydrotestosterone. Proper staging of prostate cancer is particularly important in high-risk primary disease before embarking on radical prostatectomy or radiation therapy. PET with 11C choline or acetate, but not with FDG, appears promising for the assessment of nodal metastases. PSA relapse frequently is the first sign of recurrent or metastatic disease after radical prostatectomy or radiation therapy. PET with FDG can identify local recurrence and distant metastases, and the probability for a positive test increases with PSA. However, essentially all studies have shown that the sensitivity for recurrent disease detection is higher with either acetate or choline as compared with FDG. Although more data need to be gathered, it is likely that these two agents will become the PET tracers of choice for staging prostate cancer once metastatic disease is strongly suspected or documented. 18F fluoride may provide a more sensitive bone scan and will probably be most valuable when PSA is greater than 20 ng/mL in patients with high suspicion or documented osseous metastases. Several studies suggest that FDG uptake in metastatic prostate cancer lesions reflects the biologic activity of the disease. Accordingly, FDG can be used to monitor the response to chemotherapy and hormonal therapy. Androgen receptor imaging agents like fluorodihydrotestosterone are being explored to predict the biology of treatment response for progressive tumor in late stage disease in castrated patients. The assessment of renal masses and primary staging of renal cell carcinoma are the domain of helical CT. PET with FDG may be helpful in the evaluation of "equivocal findings" on conventional studies, including bone scan, and also in the differentiation between recurrence and posttreatment changes. The value of other PET tracers in renal cell carcinoma is under investigation. Few studies have addressed the role of PET in bladder cancer. Because of its renal excretion, FDG is not a useful tracer for the detection of primary bladder tumors. The few studies that investigated its role in the detection of lymph node metastases at the time of primary staging were largely disappointing. Bladder cancer imaging with 11C choline, 11C methionine, or 11C- acetate deserves further study.

[Prostate cancer recurrence after radical prostatectomy and salvage radiotherapy]

OBJECTIVE

To evaluate the efficacy of the radiotherapy to prostatic bed in patients with biochemical recurrence for prostate cancer after radical prostatectomy.

MATERIAL AND METHODS

We analyse the results of 292 patients underwent radical prostatectomy for localized prostate cancer T1-T2 between January 1992 and June 2003, with an average folow-up of 36 months (range 6 months to 12 years). We detect biochemical recurrence (PSA >0.20 ng/ml) in 75 (26%) patients. Of 75 patients with biochemical recurrence, 9 (12%) was diagnosed of local recurrence by the following criteria: a) The first PSA obtained 6 weeks after radical prostatectomy <0.20 ng/ml. b) The time to biochemical recurrence >6 months. c) The prostate specific antigen doubling time >6 months. d) The prostate specific antigen velocity after radical prostatectomy <0.75 ng/ml/year. e) The prostate specific antigen level after radical prostatectomy <2.5 ng/ml. The 9 patients diagnosed of local recurrence received an average dose of 56.42 Gy in the prostate bed.

RESULTS

Of all 9 patients with local recurrence, 7 (77.7%) has complete response with an average time of follow-up of 25 months (6-30 months). The time between the radiotherapy and the response, in patients with complete response, was lower than 3 months. Were not observed significant adverse effects associated to radiotherapy.

CONCLUSIONS

The salvage radiotherapy may be beneficial in select patients with local recurrence. The characteristics of prostate specific antigen elevation are useful in distinguishing men with local recurrence from those with distant metastases.

THE ROLE OF 111 INDIUM-CAPROMAB PENDETIDE IMAGING FOR ASSESSING BIOCHEMICAL FAILURE AFTER RADICAL PROSTATECTOMY

PURPOSE

Conventional imaging modalities, such as computerized tomography and magnetic resonance imaging, lack sensitivity and specificity for detecting recurrent prostate cancer after radical surgery. We evaluated the role of the indium-capromab pendetide scan, otherwise known as the ProstaScint (Cytogen Corp., Princeton, New Jersey) scan, in this setting.

MATERIALS AND METHODS

A retrospective review was performed of 42 patients undergoing ProstaScint imaging for biochemical progression after radical prostatectomy. Of these patients 16 (38.1%) subsequently completed a course of salvage radiation therapy.

RESULTS

Median prostate specific antigen (PSA) immediately prior to ProstaScint imaging was 1.2 ng/ml (range 0.2 to 4.8). Abnormal accumulation on the ProstaScint scan was detected in 36 patients (85.7%). Of the 16 patients undergoing salvage radiation therapy 15 had uptake isolated to the prostatic fossa on ProstaScint imaging. Ten of these 15 patients (66.7%) achieved undetectable PSA after radiation therapy, while 5 (33.3%) had little or no response. Using American Society for Therapeutic Radiology and Oncology criteria 3 of 10 responders had relapse after an average of 9 months. The remaining 7 patients remained biochemically free of disease at last followup.

CONCLUSIONS

ProstaScint imaging is capable of detecting recurrent prostate cancer at low PSA levels. However, only 7 of 15 men (46.7%) with ProstaScint uptake isolated to the prostatic fossa showed a durable response to salvage radiation therapy. Based on these findings patients might be better treated based on the rate of increase in PSA rather than on routine scanning with this test.